Anaerobic granulation of single culture Clostridium beijerinckii

Abstract This study utilizes Clostridium beijerinckii P260, an anaerobic bacterium capable of acetone-butanol-ethanol (ABE) production, as model bacteria to test the hypothesis that single culture anaerobic granulation can be achieved in accordance with the biogranulation theory developed from the mixed culture studies. After four months of cultivation, C. beijerinckii granules formed under the selection pressure of a selective settling velocity at 9.0 m h-1 in a sequential batch reactor. These C. beijerinckii granules possess excellent settleability and exceptionally high cell and enzyme concentrations, which demonstrate promising potential in the application for high-rate fermentation and separation of value-added products. However, C. beijerinckii granules only accounted for 25% of the cell mass in the sequential batch reactor (SBR), leaving the rest 75% still in the form of planktonic cells, which indicate an incomplete anaerobic granulation. The lack of ideal feast and famine conditions in the cyclic SBR operation was regarded as the reason. Future research should focus on the optimization of the bioreactor operation to create optimal conditions for inducing the phenotype switch from planktonic to granulated growth mode.